A NEW DESIGN FOR A MAGNETIC LEVITATION SYSTEM
Magnetostatic analysis system, existing in the Workbench Ansys, and Maxwell 3D of the electromagnetics package.
In the first place, the geometry was created in Solidworks, since it is user-friendly software to create complex designs. Then, the geometry was imported in IGS or STEP format to Workbench Ansys, where the materials of each component were defined. Since different materials interact differently with magnetic fields, bringing more variables into the project, it was chosen materials which have a reduced impact on magnetic forces (Hilzinger and Rodewald 2013).
These materials are paramagnetic and have good mechanical properties that guarantee a safe usage, ending up using aluminum for the supports united to the structure intended to levitate and stainless steel for the rails. Regarding the magnets, it was chosen neodymium magnets, since they are the most powerful permanents magnets and can operate at higher temperature scales (Coey 2002), with a magnetization of grade N42. It is also important to emphasize that the top support of the structure was dimensioned regarding the tensions involved and possible deformations. It was also considered the thermal expansion of aluminum when subjected to variations of temperature it would be normally subjected when used in a house front.
Once the material selection is done, the simulation parameters were input. A region of air was created, distancing itself 200 mm of the edges in every direction. Using the Magnetostatic option, the static study was performed considering a general mesh of 1/3 mm associated with a refinement in critical areas. For the dynamic study, it was used the Maxwell 3D, considering a movement velocity of 60 mm/s.
After the running process of the simulations, in different equilibrium points, it is necessaire to validate the results. With that in mind, analytical methods and laboratory methods were used to verify the simulated results. As analytical methods, formulas from the classical literature like Maxwell, Gauss and Lorentz laws were taken into account. For the laboratory test, a 3D model was printed with scaled dimensions and, after the installation of the magnets, the magnetic fields were measured using Gauss probes.
RESULTS AND CONCLUSIONS
Fig.1 shows the created and optimized design for a magnetic levitation system with horizontal movement, using SolidWorks software. The system is projected to have an air gap of 5 mm, constant in the horizontal direction, and variable in the vertical direction, since the vertical gap depends on the weight lifted. It is also easy to substitute the magnets used if we intend greater lifting forces. The top rail is expected to be fixedly in a wall or some other stable structure, supporting the magnetic forces, while the lower rail can be mounted on the floor or embedded to be hidden, resulting in a more appealing appearance.
Due to the difficulty created by the determination of the magnetic fields and the lift forces created, it is important to establish certain operating ranges to a series of magnets, in order to prevent the necessity of calculation new magnetic fields and their lift forces.
Fig. 1 - Magnetic Levitation System a) full view b) cut view, top rail c) cut view, lower rail.
The present configuration is designed to support 215 kg/m up to 280 kg/m. The biggest gap between the rails and the levitating structure is for the lowest weight (10 mm). The air gap is, also, as lowest as possible (0.2 mm) to the higher mass.
It is recommended using an air gap of 5 mm for the most stable configuration, corresponding to a levitation force of 226 kg/m. These results were validated by the analytical calculus, which was 240 kg/m for the air gap of 5 mm. The difference was small, only 5%, and can be explaining with the mesh used in the simulations. If the mesh was more refined, the simulated results would certainly be even more coherent. However, that was not possible because of the limitation of hardware resources.
The magnetic flux of the designed system is represented in Fig.2, where the maximum value is 0.935 T. This value does not represent a risk to humans, and therefore this type of structures can be implemented in offices, houses and similar environments.
Fig. 2 - Magnetic Flux Density of the designed system
The design can also incorporate a system to automate the horizontal movement of the levitating structure using electromagnets (Long et al. 2011, Nam and Long 2013). This subject will be further analyzed and tested using computational mechanics and compared with conventional methods to evaluate its efficiency.
ACKNOWLEDGMENTS
Authors gratefully acknowledge the Engineering Faculty of University of Porto (FEUP), the Department of Mechanical Engineering (DeMEC) of FEUP, the Institute of Science and Innovation in Mechanical and Industrial Engineering (LAETA-INEGI) and the Centre for Nanotechnology and Smart Materials (CeNTI).
REFERENCES
Cazacu E, Maricaru M, Stanciulescu A, Stanculescu M. Escaping from Earnshaw Theorem,2014, pp. 59-65.
Coey JMD. Permanent magnet applications. Journal of Magnetism and Magnetic Materials, 2002, 248, p. 441–456
Hilzinger R, Rodewald W. Magnetic Materials: Fundamentals, Products, Properties, Applications. Wiley, 2013.
Hyung-Suk H, Dong-Sung K. Magnetic Levitation, 2016.
Long Z, He G, Xue S. Study of EDS & EMS Hybrid Suspension System With Permanent-Magnet Halbach Array. IEEE Transactions on Permanent-Magnetics, 2011, 47, p. 4717-4724.
Nam K, Long G. Dynamic modelling of electromagnetic suspension system. Journal of Vibration and Control, 2013, p. 729-741.
Reusch MF. A problem related to Earnshaw’s theorem. IEEE Transactions on Magnetics, 1994, 30, p. 1324–1326.
Yaghoubi H. The Most Important Maglev Applications. Journal of Engineering, 2013, p. 1-19.
EXPERIMENTAL MODAL ANALYSIS OF A FRICTION WELDED Al 6013-Al 7075 BIMATERIAL BEAM
Erhan Baysal1, Oguz Kocar2,,3, H. Alper Ozyigit2,3, Mehmet Yetmez3(*)
1Alapli Vocational School, Zonguldak Bulent Ecevit University, 67850 Zonguldak, Turkey
2Department of Mechatronics Engineering, Bulent Ecevit University, 67100 Zonguldak, Turkey
3Department of Mechanical Engineering, Bulent Ecevit University, 67100 Zonguldak, Turkey
(*)Email: [email protected]
ABSTRACT
In this study, modal analysis of a friction welded Al6013-Al7075 bimaterial aluminum alloy beam is considered. For this purpose, two different friction welding parameters (i.e., rotational speed and welding pressure) and two constant friction welding parameters (i.e., friction pressure and contact time) are taken into account. Effects of the speed and the welding pressure on the vibration characteristics/structural performances are examined experimentally. Vibration tests are performed to present free vibration characteristics of the bimaterial aluminum alloy beams under free-free boundary conditions. Results are given in tabular and graphical forms.
Keywords: friction welding, bimaterial, modal analysis, displacement response function.
INTRODUCTION
There are many studies on friction welded materials in structures. On one hand, according to mechanical control of a friction welded beam, design works indicate that the boundary conditions are very important key whether natural frequencies of a component of the beam tend to be reduced by dissimilar material zone. Many procedures are used to analysis modal stresses of such those structures with respect to optimization procedures (Vigneshwar, 2018). On the other hand, it can be noted that due to the bimaterial effect, behavior of displacement response function is of great importance. Normalized fundamental natural frequency, normalized displacement response function and normalized damping ratio values with respect to each material are actually main important parameters of a friction welded Al 6013-Al 7075 bimaterial aluminum alloy beam to understand variations of vibration characteristics in frequency domain (Ahmad, 2009).
In this study, modal analysis of a friction welded Al6013-Al7075 bimaterial aluminum alloy beam is considered. For this purpose, two different friction welding parameters (i.e., rotational speed and welding pressure) and two constant friction welding parameters (i.e., friction pressure and contact time) are taken into account. Effects of the speed and the welding pressure on the vibration characteristics/structural performances are examined experimentally. Vibration tests are performed to present free vibration characteristics of the bimaterial aluminum alloy beams under free-free boundary conditions.
MATERIALS AND METHOD
Friction welded Al6063-Al7075 bimaterial beams possess welding location at the middle of the beams. Each circular bimaterial beam with 30 mm in diameter is 300 mm in length.
Consequently, half of the beam is Al6063 and the other part is Al7075. According to friction welding parameters, eight bimaterial beam groups are taken into consideration. Details of the welding parameters of the bimaterial beam groups are given in Table 1.
Table 1 – Friction welding parameters of the bimaterial beam groups.
Group
# Welding pressure
(MPa) Friction pressure
(MPa) Contact time
(s) Rotational speed (rpm)
1 3 1.4 10 1000
2 1 1.4 10 1000
3 5 1.4 10 1000
4 10 1.4 10 1000
5 3 1.4 10 2000
6 1 1.4 10 2000
7 5 1.4 10 2000
8 10 1.4 10 2000
Vibration measurements are conducted such a way that an impact hammer with a force transducer (Model No: 5800B2, Dytran Instruments, Inc., USA) is used to excite the welded Al6063-Al7075 bimaterial beams through the selected node. After the excitations, the responses are obtained by an accelerometer (Model No: 3093B, Dytran Instruments, Inc., USA). The vibration measurements are completed using a microprocessor-based data acquisition system, namely SoMat™ eDAQ-lite and nCode GlyphWorks software (HBM, Inc., USA).
RESULTS AND CONCLUSION
Mean values of all results are normalized by the results of control groups Al6013 cylindrical aluminium beam (w=4.98 Hz, X(w)= 10.4E-9 and z=0.95 Hz/Hz) and Al7075 cylindrical aluminium beam (w=4.92 Hz, X(w)= 14.4E-9 and z=0.97 Hz/Hz) respectively.
Figure 1. Variation of fundamental natural frequency values with the bimaterial beam groups.
Figure 2. Variation of displacement response function values with the bimaterial beam groups.
Variation of fundamental natural frequency values with the bimaterial beam groups are given in Figure 1. It is clearly seen that (i) rotational speed influences the effect of welding pressure, (ii) variation of welding pressure does not affect the fundamental natural frequency under rotational speed of 2000rpm, (iii) variation of welding pressure directly affect the fundamental natural frequency in a fluctuating trend under rotational speed of 1000 rpm.
Variation of displacement response function values with the bimaterial beam groups are given in Figure 2. It is noted that (i) rotational speed influences the effect of welding pressure, (ii) variation of welding pressure affect the displacement response function values linearly under rotational speed of 2000rpm, (iii) similar with the behavior in Figure 1, variation of welding pressure affect the displacement response function values in a fluctuating trend under rotational speed of 1000 rpm.
Figure 3. Variation of damping ratio values with the bimaterial beam groups.
Variation of damping ratio values with the bimaterial beam groups are given in Figure 3. It is concluded that (i) rotational speed influences the effect of welding pressure, (ii) variation of welding pressure affect the damping ratio values in sinusoidal trend under rotational speed of 2000rpm, (iii) similar to the behavior in both Figure 1 and 2, variation of welding pressure affect the displacement response function values in a fluctuating trend under rotational speed of 1000 rpm.
REFERENCES
Vigneshwar M, Selvamani ST, Hariprasath P, Palanikumar K. Analysis of mechanical, metallurgical and fatigue behaviour of friction welded AA6061-AA2024 dissimilar aluminium alloys in optimized condition. Materials Today: Proceedings, 2018, 5, p.7853-7863.
Ahmad Z, Abdul Aleem BJ. The effect of inhibitors on the susceptibility of Al 6013/SiC interface to localized corrosion. Journal of Materials Engineering and Performance, 2009, 18, p.129-136.